Inhibition of Na+, K+-Stimulated ATPase in the Cochlea of the Guinea PIG: A Potential Cause of Disturbed Inner Ear Function in Terminal Renal Failirre

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Abstract
The influence of chronic renal failure upon Na+,K+-ATPase in the inner ear of guinea pigs was studied due to the frequent occurrence of sensorineural hearing loss in patients with chronic renal insuficiency. Na+,K+-activated ATPase was defined as the ouabain-sensitive part of total ATPase. Its activity was obtained in the presence of Na, K and Mg. A significant reduction of Na+,K+-activated ATPase was found in the inner ear of uremic animals. Such inhibition was demonstrated as early as 12 h after subtotal nephrectomy. An inverse correlation was found between serum creatinine levels and Na+,K+-activated ATPase. A similar inhibition of Na+,K+-activated ATPase in uremia was found in other tissues (erythrocytes, renal tubules, intestinal mucosal cells and sarcolemma). Na+,K+-ATPase in the cochlea plays a key role in the maintenance of cochlear cationic gradients. Inhibition of this enzyme system may contribute to the inner ear dysfunction in uremia.